1. Field of the Invention
The present invention relates to a camera module, and in particular, to an apparatus and method for controlling noise caused by vibration in a camera module for a mobile device.
2. Description of the Related Art
With the popularization of digital mobile devices, the roles of the digital mobile devices have changed. In particular, recent digital mobile devices serve more important roles as a personal portable communication device, and as an information processor like a personal information management device. Various additional functions satisfying such roles have been suggested for mobile devices, and the suggested functions have been implemented generally by allowing input of necessary information through a mobile device.
A camera module mounted in a mobile has been regarded as an essential element for inputting necessary image information in a portable digital camera. A camera module generally used in a mobile device moves a tens by driving a mounted Voice Coil Motor (VCM) in order to auto-focus an image.
FIG. 1 illustrates an example of a typical camera module using a VCM module”), in which a side cross-sectional view of the VCM camera module is shown. The VCM camera module consists of a spring, a permanent magnet, a coil, a carrier, etc. The VCM camera module operates to perform auto-focusing in a manner that a position of the carrier is changed by applying an electric current to the coil of the VCM.
Referring to FIG. 1, the VCM camera module includes a lens housing 109 in the shape of a cylinder extending longitudinally, a tens barrel 103 inside the lens housing 109, in which one or more focusing lenses 101 are mounted in the direction of an optical axis, and a coil 105 positioned along an outer circumference of the lens barrel 103 in the direction of the optical axis. Positioned on the outer circumference of the lens barrel 103 is a yoke having mounted therein a permanent magnet 111 facing the coil 105 to form a magnetic field. Positioned above the lens barrel 103 is a leaf spring 113 for providing an elastic force to allow a up/down rectilinear movement of the lens barrel 103 in the direction of the optical axis.
The VCM camera module structured as described above operates as follows. When an electric current in a particular direction is applied to the coil 105, a drive force is generated by an electromagnetic force generated between the coil 105 and the permanent magnet 111 facing the coil 105. According to the Fleming's Left Hand Rule, a force urging the lens barrel 103 to rectilinearly move up and down in the direction of the optical axis is generated by the applied electric current. The generated force is proportional to the intensity of the applied electric current. By adjusting the intensity of the applied electric current, the position of the lens barrel 103 and the focus of the lens 101 are adjusted. In other words, a magnetic field is formed when an electric current flows through the coil 105, and the generated magnetic field is moved by its repulsive force against the permanent magnet 111. The leaf spring 113 serves to determine the position of the moving section by applying its restoring force, and when no current flows, the leaf spring 113 fixes the lens 101 so that it is forced toward the sensor.
In this state, the lens housing 109 is positioned on the sensor unit 115. The sensor unit 115 includes a Printed Circuit Board (PCB) 115a, an image sensor 115b, as an imaging device, attached onto the PCB 115a, and an InfraRed (IR) filter 115c on the image sensor 115b. A Flexible PCB (FPCB) 117 is electrically connected with a bottom of the PCB 115a. 
Recently, touch-sensitive screens have often been attached onto mobile devices such as hand-held phones, Personal Digital Assistants (PDAs), palm-sized personal computers, etc. The touch-sensitive screens are intended to promote convenience by allowing users to easily input desired information as in the conventional keyboards. Functions of a mobile device having mounted thereon a touch-sensitive screen include allowing a user to recognize a touch by sensing the moment of the touch and delivering the sensing result to a vibrating motor by a sensor to drive the vibrating motor.
Vibration of the vibrating motor is delivered to the VCM camera module through a body of the mobile device. Typically, the mobile device is designed such that vibration generated by a touch pad can be controlled when the VCM camera module operates to perform imaging in the mobile device.
However, if vibration occurs while the VCM camera module is in a stop position, because of fixation using a spring in the VCM camera module, vibration generated by the vibrating motor shakes the VCM camera module, causing the VCM camera module to be run against peripheral structures. Since the VCM camera module cannot but be shaken, vibration generated by the vibrating motor causes noise.